Vehicle hydraulic device

ABSTRACT

A vehicle hydraulic device is provided with an electric motor-driven oil pump and a shuttle valve, so that a vane pump operates smoothly, even at the start, with a backpressure applied from the electric motor-driven oil pump to the vanes. Even when the oil pressure of a working fluid discharged from the vane pump exceeds the backpressure inside vane housing grooves, the working fluid flows from a vane pump discharge oil passage to a backpressure oil passage, so that the vanes are not pushed into the housing grooves. Thus, it is possible to reduce the fluctuations in discharge amount of the vane pump due to fluctuations in oil pressure of the vane pump discharge oil passage during operation of the vane pump.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No.2015-181242 filed on Sep. 14, 2015, the entire contents of which arehereby incorporated by reference.

BACKGROUND

1. Technical Field

The present disclosure relates to a vehicle hydraulic device having avane pump as the oil pressure source, and more particularly to a vehiclehydraulic device that operates smoothly even at the start and is littleaffected by fluctuations in oil pressure of a discharge oil passageduring operation of the vane pump.

2. Description of Related Art

A vane pump driven by an engine has, inside a pump housing with asubstantially elliptical inner peripheral cam surface, for example, aplurality of variable-displacement pump chambers that are defined by arotor fitted on a rotating shaft and a plurality of vanes radiallyfitted into vane housing groves provided in the rotor. As the vanesrotate while being pressed against the inner peripheral surface of thepump housing, the volumes of the pump chambers vary and a dischargeforce is applied to a working fluid.

The force for pressing the vanes against the inner peripheral surface ofthe pump housing is derived from a rotational centrifugal force and abackpressure that presses the vanes against the inner peripheral surfaceof the pump housing inside the rotor. The working fluid discharged fromthe vane pump is used to obtain this backpressure. However, if therotation speed of the rotor is low at the start of the vane pump, thepump may fail to start smoothly. This is because, even when thecentrifugal force of the rotating vanes and the backpressure generatedby the working fluid discharged from the vane pump are combined, theforce that presses the vanes against the inner peripheral surface of thepump housing is too small.

To address this problem, Japanese Patent Application Publication No.2008-286108 discloses a technique for raising the backpressure inside avane pump at the start of the vane pump. Specifically, the oil pressureof a working fluid discharged from an electric motor-driven oil pump issupplied through a backpressure oil passage into vane housing groovesprovided inside the rotor, so that a plurality of vanes that areradially fitted into the vane housing grooves formed in the rotor arepressed against the inner peripheral surface of a pump housing. Thus,the proposed vane pump operates smoothly even at the start.

In the vane pump of JP 2008-286108 A, if the discharge pressure of thevane pump exceeds the backpressure inside the vane housing grooves, thevanes may be pushed into the housing grooves and the pressure of theworking fluid discharged from the vane pump may decrease.

SUMMARY

Having been devised in the context of these circumstances, the presentdisclosure provides a vehicle hydraulic device having a vane pump ofwhich pump chambers vary in volume to apply a discharge force to aworking fluid as vanes rotate while being pressed against the innerperipheral surface of a pump housing. The vehicle hydraulic deviceaccording to the present disclosure operates smoothly even at the startand is little affected by fluctuations in oil pressure of the dischargeoil passage during operation of the vane pump.

According to one aspect of the present disclosure, a vehicle hydraulicdevice including a vane pump, an oil pressure control circuit, anelectric motor-driven oil pump, and a shuttle valve, is provided. Thevane pump is driven to rotate by an engine. The vane pump includes apump housing, a plurality of vanes, and a rotor. The pump housing has aninner peripheral cam surface with an elliptical sectional shape. Theplurality of vanes are provided inside the pump housing. The rotorprovides vane housing grooves that house the plurality of vanes so as tobe movable in a radial direction of the rotor. The oil pressure controlcircuit includes a first discharge oil passage, a second discharge oilpassage, and a backpressure oil passage. The first discharge oil passageis configured to introduce a working fluid discharged from the vane pumpto a device other than the vehicle hydraulic device. The backpressureoil passage is configured to supply a backpressure to the plurality ofvanes inside the vane housing grooves. The electric motor-driven oilpump is configured to discharge the working fluid through the seconddischarge oil passage to the backpressure oil passage. The shuttle valveis provided at a junction of the first discharge oil passage, the seconddischarge oil passage, and the backpressure oil passage. The shuttlevalve is configured to: (i) allow the working fluid to flow from thefirst discharge oil passage to the backpressure oil passage when the oilpressure of the working fluid in the first discharge oil passagedischarged from the vane pump is higher than the oil pressure of theworking fluid in the second discharge oil passage discharged from theelectric motor-driven oil pump, and (ii) allow the working fluid to flowfrom the electric motor-driven oil pump to the backpressure oil passagewhen the oil pressure of the working fluid in the first discharge oilpassage discharged from the vane pump is equal to or lower than the oilpressure of the working fluid in the second discharge oil passagedischarged from the electric motor-driven oil pump.

According to the oil pressure control circuit as described above, thevane pump operates smoothly, even at the start of the vane pump, with abackpressure applied to the plurality of vanes by the electricmotor-driven oil pump. Moreover, even when the oil pressure in the firstdischarge oil passage fluctuates to a higher pressure during operationof the vane pump, the oil pressure in the first discharge oil passage issupplied by the shuttle valve as the backpressure for the vanes, and thevanes are pushed into the housing grooves. Thus, it is possible tosuppress a decrease in pressure of the working fluid discharged from thevane pump and realize stable operation.

In the vehicle hydraulic device, the electric motor-driven oil pump maybe configured to actuate only at a start of the engine and when atemperature of the working fluid is equal to or lower than apredetermined temperature.

According to the oil pressure control circuit as described above, theelectric motor-driven oil pump is operated only at the start of theengine and when the temperature of the working fluid is equal to orlower than a predetermined temperature. Using the electric motor-drivenoil pump thus only when necessary can reduce the usage of electricpower.

Moreover, in the vehicle hydraulic device, the oil pressure of theworking fluid discharged from the electric motor-driven oil pump maydecrease as a temperature of the working fluid rises.

According to the oil pressure control circuit as described above, theoil pressure of the working fluid discharged from the electricmotor-driven oil pump decreases as the temperature of the working fluidrises. Thus, the usage of electric power can be further reduced.

Furthermore, in the vehicle hydraulic device, the electric motor-drivenoil pump may not start when a time taken for the engine to restart afterstopping of the engine is within a predetermined time.

According to the oil pressure control circuit as described above, it ispossible to reduce the electric power consumption by preventing theactuation of the electric motor-driven oil pump when the time taken forthe engine to restart after stopping is a short time within apredetermined time, since in that case the backpressure is not alwaysreduced so much and then there is no need to actuate the electricmotor-driven oil pump.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical and industrial significance ofexemplary embodiments of the disclosure will be described below withreference to the accompanying drawings, in which like numerals denotelike elements, and wherein:

FIG. 1 is a schematic view illustrating the configuration of the majorpart of a vehicle hydraulic device of a first embodiment of the presentdisclosure;

FIG. 2 is a front view of a vane pump of the vehicle hydraulic device ofFIG. 1, with a cover thereof removed;

FIG. 3 is a schematic view illustrating the configuration of the majorpart of a vehicle hydraulic device of a second embodiment of the presentdisclosure;

FIG. 4 is a functional block diagram illustrating the major part of anelectric motor control function of an electronic controller of FIG. 3;

FIG. 5 is a flowchart illustrating the major part of the operation ofcontrolling an electric motor-driven oil pump of the vehicle hydraulicdevice of FIG. 3, i.e., illustrating the control operation for reducingthe electric power used by the vehicle hydraulic device; and

FIG. 6 is a one example of a relational map used for obtaining therequired rotation speed of the electric motor-driven oil pump accordingto the temperature of a working fluid of the vehicle hydraulic device ofthe second embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

In the following, a first embodiment of a vehicle hydraulic device ofthe present disclosure will be described in detail with reference to thedrawings.

FIG. 1 is a schematic view illustrating the configuration of a vehiclehydraulic device 10. The vehicle hydraulic device 10 includes a vanepump 14, an electric motor-driven oil pump 48, and a shuttle valve 50.The vane pump 14 supplies a working fluid to an oil pressure controldevice 12 that functions as an oil pressure control circuit. The oilpressure control device 12 consumes the working fluid of, for example, ahydraulic cylinder, such as the sheave of an automatic transmission(A/T) or a continuously variable transmission (CVT). The electricmotor-driven oil pump 48 supplies a backpressure to the vane pump 14.

The vane pump 14 is driven by the rotation of an engine 15. The vanepump 14 has a first suction port 22, a second suction port 24, a firstdischarge port 26, and a second discharge port 28. The first suctionport 22 and the second suction port 24 are ports through which theworking fluid stored in an oil pan 18 is suctioned via an oil strainer20. The first discharge port 26 and the second discharge port 28 areports through which the suctioned working fluid is discharged to theoutside of the pump. The vane pump 14 further has a first backpressuregroove 42 and a second backpressure groove 44 that supply a backpressureto a plurality of vanes 82 that suction and discharge the working fluid.The working fluid is sent from the suction ports 22, 24 to the dischargeports 26, 28 through pump chambers P provided by the vanes 82.

A vane pump discharge oil passage 30, corresponding to the firstdischarge oil passage, is connected to the first discharge port 26 andthe second discharge port 28, and the vane pump discharge oil passage 30serves as a working fluid supply passage to the oil pressure controldevice 12 through which the working fluid discharged from the firstdischarge port 26 and the second discharge port 28 is pumped to the oilpressure control device 12. The vane pump discharge oil passage 30 isalso connected to a first input port 50 a of the shuttle valve 50, andserves as a working fluid supply passage to the vane pump 14 throughwhich the working fluid discharged from the first discharge port 26 andthe second discharge port 28 is pumped to the first backpressure groove42 and the second backpressure groove 44. An electric motor-driven oilpump discharge oil passage 31, corresponding to the second discharge oilpassage, is connected to the other, second input port 50 b of theshuttle valve 50, and an output port 50 c of the shuttle valve 50 isconnected to a backpressure oil passage 36.

A suction oil passage 34 connects the first suction port 22 and thesecond suction port 24 of the vane pump 14 to the oil pan 18 via the oilstrainer 20 such that the working fluid stored in the oil pan 18 issuctioned to the first suction port 22 and the second suction port 24.The suction oil passage 34 also connects the electric motor-driven oilpump 48 to the oil pan 18 via the oil strainer 20 such that the workingfluid stored in the oil pan 18 is suctioned to the electric motor-drivenoil pump 48. A return oil passage 32 returns the working fluid of theoil pressure control device 12 to the suction oil passage 34 of the vanepump 14.

FIG. 2 is a front view of the vane pump 14 of the vehicle hydraulicdevice 10, with a pump cover thereof removed. The vane pump 14 iscomposed of a body 68, a cam ring 70, a side plate 66, a rotor 74, apump shaft 76, and the pump cover (not shown). The body 68 is providedwith a substantially columnar recess 16. The cam ring 70 has asubstantially cylindrical shape, and is fitted inside the recess 16 soas to be unable to rotate relative to the body 68. The cam ring 70corresponds to the pump housing, and is therefore also called the pumphousing. The side plate 66 has a disc shape, and is mounted so as to beinterposed between a bottom wall surface of the recess 16 of the body 68and the cam ring 70, with one flat surface and the other flat surface ofthe side plate 66 in contact with the bottom wall surface of the recess16 and a substantially circular one end surface of the cam ring 70,respectively. The rotor 74 has a columnar shape, and is housed such thatthe outer peripheral surface faces an inner peripheral cam surface 78 ofthe cam ring 70 with a small space therebetween and that one end surfacein the direction of a rotational axis can come into sliding contact withthe other flat surface of the side plate 66. The pump shaft 76 is fixedto the rotor 74 coaxially with the rotational axis of the rotor 74, isrotatably supported on the body 68, and rotates the rotor 74 in thedirection of the arrow indicated in FIG. 2, i.e., in the clockwisedirection, according to the driving of a driving source, such as theengine 15. The pump cover is fastened to the body 68 so as to cover theopening of the recess 16 while being in contact with the substantiallycircular other end surface of the cam ring 70 and able to come intosliding contact with the other end surface of the rotor 74 in the axialdirection.

The cam ring 70 has the inner peripheral cam surface 78 that is theinner peripheral surface with a substantially elliptical sectionalshape. The rotor 74 includes slits 80, corresponding to the plurality ofvane housing grooves, that are formed over the entire axial length ofthe outer peripheral surface, radially from a center part in the radialdirection toward the outer peripheral surface at regular intervals inthe circumferential direction, and the plurality of rectangular,plate-shaped vanes 82 that are fitted into the slits 80. Since the slits80 house the vanes, the slits 80 are also called vane housing grooves.The vane 82 is inserted into the slit 80 such that the side surfaces ofthe vane 82 in the circumferential direction of the rotor 74 can slidein the radial direction of the rotor 74 over inner walls of the slit 80facing the vane 82; that the side surfaces of the vane 82 in the axialdirection come into sliding contact with the other end surface of theside plate 66 and an inner wall surface of the pump cover, respectively;and that the radially outer end surface of the vane 82 can slide overthe inner peripheral cam surface 78 of the cam ring 70.

When the rotor 74 is driven to rotate, the vane 82 is pushed out towardthe radially outer side of the rotor 74 from the inner wall of the slit80 under the backpressure from the first backpressure groove 42 and thesecond backpressure groove 44, so that the radially outer end surface ofthe vane 82 is pressed against the inner peripheral cam surface 78 ofthe cam ring 70 and, in this state, slides over the inner peripheral camsurface 78 in the rotation direction of the rotor 74. Thus, theplurality of pump chambers P are defined by the side surfaces of theadjacent vanes 82 facing each other in the circumferential direction,the inner peripheral cam surface 78, the outer peripheral surface of therotor 74, the other end surface of the side plate 66, and the inner wallsurface of the pump cover. Since the inner peripheral cam surface 78 hasa substantially elliptical shape, as the rotor 74 makes one rotation,the vane 82 reciprocates twice inside the slit 80 in the radialdirection of the rotor 74, so that the volume of the pump chamber Pincreases and decreases twice.

In the side plate 66 and the body 68, the pair of first suction port 22and second suction port 24 communicating with the pump chambers P, whichincrease in volume according to the rotation of the rotor 74, are formedacross the pump shaft 76 so as to straddle both the side plate 66 andthe body 68. In the side plate 66 and the body 68, the pair of firstdischarge port 26 and second discharge port 28 communicating with thepump chambers P, which decrease in volume according to the rotation ofthe rotor 74, are formed across the pump shaft 76 so as to straddle boththe side plate 66 and the body 68. The first discharge port 26 islocated on the front side in the rotation direction of the rotor 74relative to the first suction port 22. The second discharge port 28 islocated on the front side in the rotation direction of the rotor 74relative to the second suction port 24. It is also possible to form theports 22, 24, 26, 28 only in the side plate 66, instead of forming theseports so as to straddle both the side plate 66 and the body 68.

The side plate 66 communicates with the inner peripheral ends of theslits 80, into which the vanes 82 defining the pump chambers P arefitted, between the first suction port 22 and the first discharge port26. The first backpressure groove 42 and the second backpressure groove44 that supply a backpressure for pressing the vanes 82 against theinner peripheral cam surface 78 are formed in a semi-annular shape inthe circumferential direction of the rotor 74. The first backpressuregroove 42 and the second backpressure groove 44 communicate with thebackpressure oil passage 36.

When the vane pump 14 is started according to the driving of the engine15 and the rotor 74 is rotated in the clockwise direction in FIG. 2, theworking fluid inside the oil pan 18 is suctioned through the suction oilpassage 34 into the first suction port 22 and the second suction port24, and carried to each pump chamber P of the vane pump 14 of which thevolume increases gradually as the rotor 74 rotates. As the rotor 74rotates and the volumes of the pump chambers P decrease accordingly, theworking fluid suctioned into the pump chambers P is discharged throughthe first discharge port 26 and the second discharge port 28 to the vanepump discharge oil passage 30. When an electric motor 52 dedicated tothe electric motor-driven oil pump 48 is driven along with the start ofthe engine 15 and the electric motor-driven oil pump 48 is startedaccordingly, the working fluid inside the oil pan 18 is suctionedthrough the suction oil passage 34 into the electric motor-driven oilpump 48, and discharged to the electric motor-driven oil pump dischargeoil passage 31 communicating with the second input port 50 b of theshuttle valve 50.

The vane pump discharge oil passage 30 and the electric motor-driven oilpump discharge oil passage 31 communicate respectively with the firstinput port 50 a and the second input port 50 b of the shuttle valve 50.The backpressure oil passage 36 communicates with the output port 50 cof the shuttle valve 50. When the oil pressure of the working fluid inthe vane pump discharge oil passage 30 discharged from the vane pump 14is higher than the oil pressure of the working fluid in the electricmotor-driven oil pump discharge oil passage 31 discharged from theelectric motor-driven oil pump 48, the shuttle valve 50 allows theworking fluid to flow from the vane pump discharge oil passage 30 to thebackpressure oil passage 36. When the oil pressure of the working fluidin the vane pump discharge oil passage 30 discharged from the vane pump14 is equal to or lower than the oil pressure of the working fluid inthe electric motor-driven oil pump discharge oil passage 31 dischargedfrom the electric motor-driven oil pump 48, the shuttle valve 50 allowsthe working fluid to flow from the electric motor-driven oil pumpdischarge oil passage 31 to the backpressure oil passage 36. Thus, thebackpressure for pressing the vanes 82 defining the pump chambers P ofthe vane pump 14 against the inner peripheral cam surface 78 of the camring 70 is maintained.

Thus, the vehicle hydraulic device 10 of this embodiment is providedwith the electric motor-driven oil pump 48 and the shuttle valve 50, sothat the vehicle hydraulic device operates smoothly, even at the start,as a backpressure is applied from the electric motor-driven oil pump 48to the vanes 82. Moreover, even when the oil pressure of the workingfluid discharged from the vane pump exceeds the backpressure inside theslits 80 during operation of the vane pump 14, the working fluid flowsfrom the vane pump discharge oil passage 30 to the backpressure oilpassage 36, so that the vanes 82 are pushed into the slits 80 and thepressure of the working fluid discharged from the vane pump 14 does notdecrease. Thus, it is possible to suppress the decrease in dischargeamount of the vane pump 14 even if the oil pressure in the vane pumpdischarge oil passage 30 fluctuates to a higher pressure duringoperation of the vane pump 14.

EMBODIMENT 2

Next, a second embodiment of the present disclosure will be described.In the following second embodiment, those parts that have substantiallythe same functions as in the first embodiment will be denoted by thesame reference signs and the detailed description thereof will beomitted. A vehicle hydraulic device 100 of the second embodiment isdifferent from the vehicle hydraulic device 10 of the first embodimentin that the electric motor-driven oil pump 48 is operated only at thestart of the engine 15 and when the temperature of the working fluid isequal to or lower than a predetermined temperature, and in that the oilpressure of the working fluid discharged from the electric motor-drivenoil pump 48 is reduced as the temperature of the working fluid rises.Only these differences will be described in detail below using FIG. 3 toFIG. 6.

FIG. 3 is a schematic view illustrating the configuration of the vehiclehydraulic device 100 of the second embodiment of the present disclosure.The configuration of the vehicle hydraulic device 100 is the same as theconfiguration of the vehicle hydraulic device 10 shown in FIG. 1, i.e.,includes the electric motor 52, which drives the electric motor-drivenoil pump 48, in addition to the vane pump 14 that supplies the workingfluid to the oil pressure control device 12 that consumes the workingfluid of, for example, a hydraulic cylinder, such as the sheave of anA/T or a CVT, the electric motor-driven oil pump 48 that supplies abackpressure to the slits 80 of the vane pump 14, the shuttle valve 50,the oil pan 18, the oil strainer 20, and the oil passages for theworking fluid to flow through. However, the vehicle hydraulic device 100is different from the vehicle hydraulic device 10 in that a temperaturesensor 54 that detects the temperature of the working fluid, and anelectronic controller 56 that controls the electric motor 52 on thebasis of the temperature detected by the temperature sensor 54 areprovided. The electric motor 52 is driven through a control signal fromthe electronic controller 56 and actuates the electric motor-driven oilpump 48 to supply the working fluid to the electric motor-driven oilpump discharge oil passage 31. The electronic controller 56 isconfigured with a so-called microcomputer that includes, for example, aCPU, a RAM, a ROM, and an input-output interface, and the CPU executesoutput control of the engine 15, speed change control of an automatictransmission (not shown), etc. by processing signals according to aprogram that is stored in the ROM in advance using the temporary storagefunction of the RAM.

In the vehicle hydraulic device 100 of this embodiment, to reduce theelectric power used for actuating the electric motor-driven oil pump 48,for example, the electric motor 52 is driven only at the start of theengine 15 and when the temperature of the working fluid is equal to orlower than a preset temperature, so as to restrict the actuation of theelectric motor-driven oil pump 48. Moreover, to reduce the electricpower used for actuating the electric motor-driven oil pump 48, forexample, the oil pressure of the working fluid discharged from theelectric motor-driven oil pump 48 is reduced as the temperature of theworking fluid rises.

FIG. 4 is a functional block diagram illustrating the major part of anelectric motor control function of the electronic controller 56, andincluding an engine start determination unit 62, a working fluidtemperature determination unit 60, and an electric motor control unit58. The engine start determination unit 62 determines whether or not theengine 15 is at start. The working fluid temperature determination unit60 determines whether or not a working fluid temperature TOIL is equalto or lower than a preset working fluid criterion temperature Te. Theelectric motor control unit 58 actuates the electric motor 52 by sendingan electric motor control signal SM to the electric motor 52 on thebasis of the determination of the engine start determination unit 62 andthe working fluid temperature determination unit 60. The engine startdetermination unit 62 may determine whether or not the time from whenthe engine 15 is driven and stopped last time until the engine 15 isdriven this time, i.e., the time taken to restart, is within apredetermined time, and the electric motor control unit 58 may controlso as not to start the electric motor 52 if the time taken to restart iswithin the predetermined time.

FIG. 5 is a flowchart of the major part of the operation of controllingthe electric motor-driven oil pump 48 performed by the electroniccontroller 56 of FIG. 3, i.e., the control operation for reducing theelectric power used by the vehicle hydraulic device 100. This operationis executed repeatedly.

In FIG. 5, in step (hereinafter “step” will be omitted) S1 correspondingto the engine start determination unit 62, it is determined whether ornot the engine 15 is at start. The current routine ends if thedetermination result in S1 is negative. If the determination result isaffirmative, it is determined in S2, corresponding to the working fluidtemperature determination unit 60, whether or not the working fluidtemperature TOIL is equal to or lower than the preset working fluidcriterion temperature Te on the basis of the signal from the temperaturesensor 54. The current routine ends if the determination result in S2 isnegative. If the determination result is affirmative, in S3corresponding to the electric motor control unit 58, the electric motor52 is actuated on the basis of the electric motor control signal SM fromthe electric motor control unit 58 and the electric motor-driven oilpump 48 is driven. Under such control, the actuation of the electricmotor-driven oil pump is restricted and the electric power used by thevehicle hydraulic device 100 is reduced.

FIG. 6 is one example of a relation (map) stored in advance that is usedby the electric motor control unit 58 to obtain the working fluidtemperature TOIL (° C.) and the rotation speed (rpm) of the electricmotor-driven oil pump 48 required at a given working fluid temperature.Specifically, as the temperature of the working fluid rises, the oilpressure of the working fluid discharged from the electric motor-drivenoil pump 48 is reduced, i.e., the rotation speed of the electricmotor-driven oil pump 48 is reduced, and thus the electric power used bythe vehicle hydraulic device 100 is reduced.

While the present disclosure has been described in detail with referenceto the drawings, the present disclosure can also be implemented in otherembodiments, and various modifications can be made within the scope ofthe disclosure.

For example, in the vane pump 14 of the first embodiment and the secondembodiment, the cam ring 70 having the inner peripheral cam surface 78is fitted in the recess 16 of the body 68. However, the presentdisclosure is not limited thereto, and, for example, the cam ring may beomitted by forming the inner peripheral cam surface 78, facing the outerperipheral surface of the rotor 74, directly on the inner peripheralsurface of the recess 16 of the body 68.

In the vane pump of the first embodiment and the second embodiment, theplurality of discharge ports 26, 28 communicate with the oil pressurecontrol device 12 and the working fluid is supplied thereto. However,the working fluid may be supplied from the plurality of discharge ports26, 28 to separate oil pressure control devices. In that case, aplurality of shuttle valves 50 may be used respectively for theplurality of discharge ports 26, 28, or only one shuttle valve 50 may beused to control the oil pressure of the working fluid in thebackpressure oil passage 36 to be supplied to the vanes 82.

What is claimed is:
 1. A vehicle hydraulic device comprising: a vanepump that is driven to rotate by an engine, and the vane pump includinga pump housing, a plurality of vanes, and a rotor, the pump housinghaving an inner peripheral cam surface with an elliptical sectionalshape, the plurality of vanes being provided inside the pump housing,the rotor providing vane housing grooves that house the plurality ofvanes so as to be movable in a radial direction of the rotor; an oilpressure control circuit including a first discharge oil passage, asecond discharge oil passage, and a backpressure oil passage, the firstdischarge oil passage being configured to introduce a working fluiddischarged from the vane pump to a device other than the vehiclehydraulic device, the backpressure oil passage being configured tosupply a backpressure to the plurality of vanes inside the vane housinggrooves; an electric motor-driven oil pump configured to discharge theworking fluid through the second discharge oil passage to thebackpressure oil passage; and a shuttle valve provided at a junction ofthe first discharge oil passage, the second discharge oil passage, andthe backpressure oil passage, the shuttle valve being configured to: (i)allow the working fluid to flow from the first discharge oil passage tothe backpressure oil passage when the oil pressure of the working fluidin the first discharge oil passage discharged from the vane pump ishigher than the oil pressure of the working fluid in the seconddischarge oil passage discharged from the electric motor-driven oilpump, and (ii) allow the working fluid to flow from the electricmotor-driven oil pump to the backpressure oil passage when the oilpressure of the working fluid in the first discharge oil passagedischarged from the vane pump is equal to or lower than the oil pressureof the working fluid in the second discharge oil passage discharged fromthe electric motor-driven oil pump.
 2. The vehicle hydraulic deviceaccording to claim 1, wherein the electric motor-driven oil pump isconfigured to actuate, only at a start of the engine and when atemperature of the working fluid is equal to or lower than apredetermined temperature.
 3. The vehicle hydraulic device according toclaim 1, wherein the oil pressure of the working fluid discharged fromthe electric motor-driven oil pump decreases as a temperature of theworking fluid rises.
 4. The vehicle hydraulic device according to claim1, wherein the electric motor-driven oil pump does not start when thetime taken for the engine to restart after stopping of the engine iswithin a predetermined time.